1. Field of the Invention
The present invention relates to a spindle motor and a disk driving device.
2. Description of the Related Art
In accordance with the trend for the miniaturization of electronic devices such as laptop computers, external hard drives, video game consoles, or the like, a small-sized spindle motor used in a disk driving device has been thinned.
A thinned disk driving device requires a motor structure in which low voltage driving characteristics are improved. Therefore, research into a motor structure in which low voltage characteristics are improved has been actively undertaken.
A hard disk driving device includes a recording head as a component for reading information recorded on a magnetic disk and writing information thereon. The recording head is mounted on a base member of the spindle motor and moves across the face of the magnetic disk.
The recording head is driven by a voice coil motor (VCM). When the supply of power thereto is stopped, in the case in which sufficient power is not secured in the voice coil motor, the recording head remains positioned above the magnetic disk in place, such that in the case that the recording head and the magnetic disk contact each other, information recorded in the magnetic disk may be seriously damaged.
In order to solve this defect, the hard disk driving device may drive the voice coil motor using back electromotive force (B-EMF) of the spindle motor. The voice coil motor is driven, such that the recording head returns to an initial position without contacting the magnetic disk, known as emergency parking.
Here, a method of using B-EMF is as follows. Electrical energy is generated through inertial force of the magnetic disk, rotating after the supply of power is stopped during the driving of the spindle motor, and is used in the voice coil motor.
In the disk driving device according to the related art, B-EMF is not problematic. However, in a 2.5″ type disk driving device that has been miniaturized, a B-EMF securing problem has been generated. Therefore, research into a technology for securing B-EMF has been demanded.
In the following Related Art Documents, Patent Document 1 has disclosed a technology of adjusting a torque constant by adjusting a height of a stator core and a height of a rotor magnet in a 2.5″ type disk driving device having a thickness 7 mm, Patent Document 2 has disclosed a fluid interposed between a fixed member and a rotating member so as to be rotatable at a low driving current, and Patent Document 3 has disclosed a method of adjusting a torque constant using a stator core formed by molding a ferromagnetic particulate material.
These Related Art documents do not specifically disclose methods capable of reducing noise and vibrations, and securing back electromotive force enabling emergency parking while securing thrust dynamic pressure in a miniaturized disk driving device.